As one measure for copy-guarding digital broadcast programs, a “Copy One Generation” control signal indicating that recording is possible only one time is added to the digital broadcast program before encryption and broadcasting. A digital broadcast program having a “Copy One Generation” control signal added in this way can be recorded using a recording/playback apparatus that includes an appropriate copyright protection function. The recorded digital broadcast program cannot be dubbed to another device, but a transfer of the digital broadcast program is permitted.
Patent Document 1: Japanese Patent Application Publication No. 2003-228522
Non-patent Document 1: “Gendai Angou Riron (Modern Encryption Theory)” by Nobuichi Ikeno and Kenji Koyama, Institute of Electronics, Information and Communications Engineers
Non-patent Document 2: “Gendai Angou Nyuumon (Introduction to Modern Encryption)” by Eiji Okamoto, Kyoritsu Shuppan Co., Ltd.